FETAL MEMBRANESPlacentaNutrition

2011

Fetal membranes

Chorion Amnion Yolk sac Allantois They develop from zygote, however they

are not involved in embryo formation except for small part of yolk sac, that participate on gut formation

Amnion Amnionic fluid Amnioblasts,

interstitial fluid form endometrium

Embryo (before skin keratinization) – transudation from body

Umbilical cord Respiratory system,

urine

10th week – 30ml 20th week – 350ml 37th week - 700-

1000ml

Function of amniotic fluid It allows symetric growth Protects from infection Facilitates normal development of lung Protects from adhesion Protects from injury Keeps stabile temperature Alows free movement Takes place in homeostasis (electrolytes)

Failures of amnionic fluid volume

Oligohydramnion – less than 400ml - rupture of fetal membranes, renal agenesis – (Potter syndrome) - pulmonary hypoplasia, pes equinovarus, face dysmorfy

Polyhydramnion – more than 2000 ml – malformed CNS, esofageal atresia, twins, idiopatic

Yolk sac Transfer and metabolism of nutrients – as

liver Development of blood cells and vessels

-vitelline vascular system Participation on formation of primitive

gut Primordial gamets in endoderm of yolk

sac during 3rd week

Allantois Development form hindgut – evagination

into embryonic stalk - only transient Vessels – umbilical arteries and veins for

placenta supply Intraembryonic part – urachus, urinary

bladder ( ligamentum umbilicale medianum)

Placenta Fetal organ providing nutrition and many

other functions: Function:

− Metabolism (synthesis, for example glycogen)− Transport of gases and nutrients− Excretion of waste products− Production of hormones (hCG)

Embryo nutrition Nutrients supply in yolk sac (AA, lipids) Histiotrophe – secret from glandular cells

in fallopian tube, uterus, digestion of endometrium

Haematotrophe – maternal blood Organ that provide nutrition of embryo in

mammals - chorion/placenta

Placenta - structure Fetal part – chorion – chorionic plate and

chorionic villi Maternal part – endometrium – pars

functionalis – decidua basalis

Decidua Zona functionalis that is changing during

pregnancy Decidua basalis Decidua capsularis Decidua parietalis

Progesteron – cell in stroma (fibroblasts) are changed in decidual cells (content of glycogen and lipids)+ changes in vascular supply = decidual reaction

Implantation

Implantation During implantation embryo invades in

zona functionalis of endometrium Trophoblast diferentiates into

syncytiotrophoblast and cytotrophoblast Extraembryonic mesoderm adds to

cytotrophoblast

= CHORION

Development of chorionic villi Primary: Syncytiotrophoblast and

cytotrophoblast Secondary: Syncytiotrophoblast,

cytotrophoblast and extraembryonic mesoderm

Tertiary: Vessels occur in mesoderm Terctiary villi are all from 3rd week of

development

Placenta development Chorion laeve Chorion frondosum Decidua capsularis get thiner, later

disappears, chorion laeve is on the surface, it unites with decidua parietalis and obliterates uterine cavity ( week 22 -24)

Intervillous space It develops from lacunae in sytiotrophoblast

It is divided by placental septa

Maternal blood – spiral arteries in decidua basalis – uteroplacental vessels

It wash up villi – it is drained into placental veins. Fetal and maternal blood do not mix !!!

Hemocytoblasts (stem cells) may cross from embryonic to maternal blood and stay there for relatively long time (several years) -chimera

Placental circulation Umbilical arteries

-deoxygenated blood from embryonic body

Chorionic arteries branching in chorionic plate

Capillary network in chorionic villi

Placental membrana Interface between maternal and fetal

blood• Syncytiotrophoblast

• Cytotrophoblast• Connective tissue

• Endothelium of fetal capillary

After week 12 cytotrophoblast gradually disappears, vessels come near to surface and get in contact with syncytiotrophoblast

3rd trimester Nuclei of

syncytiotrophoblast form aggregations – syncytial knots that may set free

Formation of fibrinoid – it reduces placental transfer

Syncytiotrophoblast – microvilli, SER, RER, GC, mito – active synthesis

Cytotrophoblast – undifferentiated cells – mitoses

Basal membrane Continuous

endothelium

Feto-maternal junction Different genotype – necessity to supress

imunity: Maternal and fetal tissue are separted by the

cells that do not have typical superficial antigens. Hormonal changes (progesteron, glucocorticods)

– Blood - Syncytiotrophoblast

– Connective tissue – Cytotrophoblastic shell Stem - anchoring villi attach chorion to the

decidua basalis – inside cytotrophoblastic plug

Placenta Placental shape – discoid (olliformis) +

haemochorial Placental septa – rests of decidua basalis.

They separate placenta from maternal side in lobes - cotyledons

Cotyledons – contain 2 and more anchoring villi

Diameter – 15 -20 cm, thickness 2-3 cm, weight 500 to 600 g

Placental transfer Difusion Facilitated difusion Active transport Pinocytosis Other types of transfer:

Damage of placetal barrier – blood cellas Own activity – Treponema pallidum Damage due to infection - toxoplasmosa

Transfer Many substances from maternal blood

may transfer placental barrier including drugs

Nutrients – glucose, AK, fatty acids, water, vitamines, electrolytes

Hormones – only steroid unconjugates Maternal antibodies, transferin+ iron

Syntesis hCG – human chorionic gonadotropin hCS – human chorionic somato-

mammotropin/placental lactogen hCT human chorionic thyrotropin hCACTH human chorionic corticotropin Progesteron and estrogens

Placental abnormalities Atypical implatation: Placenta previa Placenta accreta Placenta percreta Placenta membranacea Placenta accessoria Atypical attachment of umbilical cord--

marginal, velamentous

Development of mbilical cord Connective stalk with umbilical arteries

and veins and allantois Ductus omphaloentericus connecting gut

with yolk sac Extraembryonic coelom Umbilicus

Developmentof umbilical cord• Length 50 cm